Painkillers can affect the kidneys, but the risk depends on the type of painkiller, how it is used, your existing health conditions, and whether other medicines or factors are putting extra strain on the kidneys.
The strongest concern is with non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen and diclofenac. NSAIDs can reduce blood flow to the kidneys and, in some people, contribute to acute kidney injury (AKI)or worsening kidney function. The risk is greater with higher or repeated exposure, existing kidney disease, dehydration and certain combinations of medicines.
Kidney problems do not always cause obvious symptoms at first. If you are worried that a painkiller may be affecting your kidneys, do not try to diagnose the problem from symptoms alone. Check what medicine you are taking, note any changes you have experienced and speak to a doctor or pharmacist.
You can also read the related guide to medicines that may cause kidney problems or browse the Symptom-Led Side Effects hub for other medicine-related symptoms.
How painkillers can be linked to kidney side effects
Your kidneys continuously filter waste and excess fluid from your blood. They also help regulate fluid balance, electrolytes and blood pressure.
Some pain medicines can interfere with these processes.
NSAIDs work partly by blocking substances called prostaglandins. Prostaglandins have several functions in the body, including helping maintain blood flow to the kidneys in situations where circulation is under strain. By reducing their effects, NSAIDs can reduce kidney blood flow in susceptible people.
This does not mean that everyone who takes an NSAID will develop kidney damage. Many people use these medicines without kidney complications. Risk becomes more important when other factors are present.
Possible painkiller categories
NSAIDs
This group is particularly relevant when researching painkillers causing kidney problems. Examples include:
- ibuprofen
- naproxen
- diclofenac
- indomethacin
- celecoxib
- meloxicam
- higher-dose aspirin used for pain or inflammation
Some are available without a prescription, while others require a prescription. Brand names vary, so checking the active ingredient is more useful than relying on the brand name alone.
Paracetamol
Paracetamol is not an NSAID and does not affect kidney blood flow in the same way. When used as directed, it is generally considered less concerning for the kidneys than NSAIDs in many situations. However, it still has important safety limits, and excessive exposure can cause serious toxicity. Long-term or excessive use of pain medicines has also historically been associated with analgesic-related kidney damage.
Do not assume this means paracetamol is automatically the right choice for you. A pharmacist or doctor can take your medical history and other medicines into account.
Prescription painkillers
Kidney function may also affect how certain prescription pain medicines are cleared from the body. When kidney function is reduced, some medicines or their active breakdown products can accumulate and increase the risk of adverse effects. This is one reason people with kidney disease may need individual medical advice about pain treatment.
Timing clues
The timing of symptoms can provide useful information for your healthcare professional, although timing alone cannot prove that a painkiller caused a kidney problem.
Possible patterns include:
- symptoms beginning after starting a new painkiller
- symptoms occurring after increasing or repeatedly using a pain medicine
- problems appearing while you are dehydrated from vomiting, diarrhoea, fever or poor fluid intake
- symptoms developing while taking several medicines that can affect kidney function
- kidney-test results changing after a medicine was started
- problems developing after frequent painkiller use over a longer period
NSAIDs may be more likely to contribute to acute kidney injury when a person is dehydrated or has low blood pressure.
If the timing seems suspicious, record it rather than trying to prove the connection yourself.
Medicines and product categories that may be associated with kidney problems
Not every product sold for pain works in the same way. Identifying the active ingredient is an important first step.
NSAID painkillers
NSAIDs are among the main medicine categories to discuss with a doctor or pharmacist when kidney safety is a concern.
People may take an NSAID for:
- headaches
- toothache
- period pain
- muscle or joint pain
- arthritis
- sprains and strains
- fever or inflammation
Kidney risk may be higher in people who already have impaired kidney function or who have other conditions affecting blood flow to the kidneys. High blood pressure, heart disease and older age can also be relevant.
Cold, flu and combination medicines
A product may contain a painkiller even when the front of the pack is marketed mainly for a cold, flu, sinus problem or another symptom.
This creates the possibility of unintentionally taking the same ingredient from more than one medicine.
Check the active ingredients on each product rather than assuming medicines with different brand names contain different drugs. If you are unsure, show all the packages to a pharmacist.
Medicines taken alongside painkillers
Kidney problems can sometimes involve several contributing factors rather than one medicine acting alone.
For example, the National Kidney Foundation identifies NSAIDs alongside certain blood-pressure medicines, including ACE inhibitors or ARBs, and diuretics as medicines that can become important in the setting of acute kidney injury risk.
This does not mean you should stop any of these medicines yourself. Prescription medicines may be essential for treating high blood pressure, heart disease or other conditions. A healthcare professional should review the combination and your individual risk.
Supplements and herbal products
Tell your doctor or pharmacist about supplements, traditional remedies and herbal products as well as conventional medicines.
Products described as “natural” are still biologically active and can have side effects or interact with medicines. If kidney problems are being investigated, your healthcare professional needs a complete list of everything you are taking.
Who may be more vulnerable to painkiller-related kidney problems?
Anyone can experience a medicine side effect, but some situations deserve extra caution.
Discuss painkiller use with a healthcare professional if you:
- already have kidney disease or reduced kidney function
- have previously had acute kidney injury
- have diabetes
- have high blood pressure
- have heart disease or heart failure
- are an older adult
- are dehydrated or have recently had significant vomiting or diarrhoea
- regularly use NSAIDs
- take several prescription and non-prescription medicines
- have recently started a new medicine that may affect kidney function
Existing kidney disease is particularly important because NSAIDs can further reduce blood flow to kidneys whose function is already impaired.
What kidney side effects could look like
Kidney injury can sometimes develop without noticeable early symptoms. Blood and urine tests may detect a problem before you feel unwell.
When symptoms do occur, possible signs of kidney dysfunction can include:
- producing noticeably less urine than usual
- swelling in the feet, ankles, legs or elsewhere
- blood in the urine
- unusual tiredness or weakness
- nausea or vomiting
- shortness of breath
- confusion or unusual drowsiness
- flank or back pain
- changes in blood pressure
These symptoms are not specific to painkiller-related kidney damage. They can have many different causes, and their presence does not prove that a medicine is responsible.
If you notice a significant change after taking a medicine, especially if symptoms are worsening, contact a healthcare professional.
Red flags: when kidney or medicine symptoms may need urgent medical attention
Some symptoms should not be managed by monitoring at home.
Seek urgent medical help if you experience:
- severe difficulty breathing
- swelling of the face, lips, tongue or throat
- fainting or loss of consciousness
- seizures
- chest pain
- a severe or rapidly spreading rash
- severe or uncontrolled bleeding
- severe confusion or marked difficulty staying awake
- very little or no urine together with worsening illness
- rapidly increasing swelling or severe shortness of breath
- symptoms after a suspected overdose
- any symptoms that are severe or rapidly getting worse
A severe allergic reaction, overdose or sudden deterioration can be an emergency regardless of whether the kidneys are involved.
For more guidance on recognising concerning reactions, see serious medication side effects and when to see a doctor for medication side effects.
What to track before speaking to a doctor or pharmacist
A clear timeline can make it much easier for a healthcare professional to assess a suspected medicine reaction.
Record the medicine details
Write down:
- the medicine’s name
- the active ingredient, if known
- whether it was prescribed or bought over the counter
- when you started using it
- when you last took it
- how frequently you have been using it
- any other painkillers, cold remedies or combination products you use
- all prescription medicines, supplements and herbal products you take
Take the packaging or patient information leaflet with you if possible.
Record the symptoms
Note:
- what you noticed
- when it began
- whether it appeared before or after starting the medicine
- whether it is improving, stable or worsening
- any change in how often or how much you urinate
- swelling of the ankles, feet or legs
- vomiting or diarrhoea
- fever or another recent illness
- whether you may have been dehydrated
Do not deliberately take another dose simply to see whether the symptom happens again.
Tell your healthcare professional about existing conditions
Mention any history of:
- kidney disease
- acute kidney injury
- high blood pressure
- diabetes
- heart disease or heart failure
- liver disease
- stomach ulcers or gastrointestinal bleeding
This context can significantly change how a doctor or pharmacist assesses the risks and benefits of a pain medicine.
What tests might a healthcare professional consider?
Symptoms alone cannot reliably confirm kidney damage.
Depending on the situation, a clinician may assess kidney function using blood and urine tests. Blood testing can include creatinine, which is used when estimating kidney filtration, while urine testing can provide additional information about kidney health.
Other investigations may be needed depending on the symptoms and medical history.
Do not assume that normal urine output means kidney function is definitely normal. Some kidney problems cause few or no early symptoms.
What not to do without medical advice
Concern about kidney side effects can make it tempting to change several things at once. That can make the situation harder to assess and, in some cases, create additional risks.
Do not stop important prescription medicines on your own
If a prescription painkiller or another medicine is suspected, contact the prescribing doctor or a pharmacist for guidance.
Stopping some medicines abruptly can be harmful. The safest action depends on the medicine, why it was prescribed and how serious the suspected reaction is.
Do not take extra doses
Taking more than the recommended or prescribed amount does not necessarily give better pain relief and can increase the risk of toxicity.
If you think you have taken an overdose, seek urgent medical help rather than waiting for symptoms to develop.
Do not combine painkillers without checking the ingredients
Two differently branded products may contain the same active ingredient or medicines from the same drug class.
This is especially easy to miss with cold, flu, headache and combination pain products.
A pharmacist can check the ingredients for you.
Do not assume an OTC medicine is risk-free
“Over the counter” means a medicine can be supplied without a prescription. It does not mean the medicine cannot cause significant side effects.
MedlinePlus advises people with kidney disease, high blood pressure, heart disease and certain other conditions to speak to a healthcare professional before using OTC NSAIDs.
Do not rely on symptoms alone
Kidney disease can be silent, and symptoms such as swelling, fatigue or changes in urination can also result from conditions unrelated to painkillers.
If kidney injury is a concern, professional assessment and appropriate testing are more reliable than trying to diagnose yourself online.
How can you reduce avoidable medicine-related risk?
The safest approach depends on your individual health and the reason you need pain relief, but several practical habits can help reduce avoidable medication errors.
- Read the package and patient information leaflet.
- Check the active ingredient.
- Follow the prescribed or labelled directions.
- Avoid unintentionally taking the same active ingredient from several products.
- Tell your healthcare professional if you use painkillers frequently.
- Keep an up-to-date list of prescription medicines, OTC products and supplements.
- Ask a pharmacist before adding another painkiller if you take regular medication.
- Tell a healthcare professional if you have kidney disease or previously abnormal kidney tests.
NIDDK specifically recommends keeping an up-to-date medicine and supplement list and discussing OTC medicines with healthcare professionals when kidney safety is a concern.
Related side-effect guides and reporting options in South Africa
If your concern is specifically whether a medicine may be affecting kidney function, the medicine-causing-kidney-problems guide provides a broader look at medicine-related causes.
You can also explore medication side effects if you are experiencing a different reaction or trying to understand a medicine’s overall side-effect profile.
Reporting a suspected medicine side effect to SAHPRA
In South Africa, suspected adverse reactions can be reported to the South African Health Products Regulatory Authority (SAHPRA).
Patients and members of the public can report suspected reactions, and SAHPRA provides electronic reporting routes as well as adverse drug reaction reporting forms. SAHPRA’s Med Safety system also allows members of the public and healthcare professionals to submit suspected medicine reactions.
Reporting does not mean you have proved that a medicine caused the problem. Pharmacovigilance systems collect suspected reactions so medicine-safety patterns can be assessed.
See our guide on how to report side effects in South Africa for the practical steps.
What information should you record?
Useful information may include:
- the suspected medicine and active ingredient
- when you started and stopped using it
- when the symptoms began
- a description of the reaction
- other medicines or supplements being used
- relevant medical conditions
- any medical treatment or tests related to the reaction
SAHPRA’s adverse-reaction reporting guidance recognises reports involving prescription medicines as well as OTC medicines.
Reporting a suspected reaction is separate from getting medical treatment. If you are unwell, seek medical advice first.
Frequently asked questions
Are kidney problems a common side effect of painkillers?
It depends on the painkiller and the person taking it.
NSAIDs can affect kidney blood flow and are a recognised cause of acute kidney injury in susceptible people, but most short-term users will not automatically develop kidney damage. Risk is more important with existing kidney disease, dehydration, higher or repeated exposure, older age and certain other medicines.
If you use painkillers regularly, discuss this with a doctor or pharmacist rather than assuming continued OTC use is harmless.
Can ibuprofen damage the kidneys?
Yes, ibuprofen is an NSAID and can contribute to kidney injury in some circumstances. The risk can increase in people with reduced kidney function or when someone is dehydrated or otherwise medically vulnerable.
This does not mean kidney damage occurs every time someone takes ibuprofen.
Can diclofenac affect the kidneys?
Diclofenac is also an NSAID. Oral diclofenac is among the NSAIDs associated with acute kidney injury risk, particularly when other risk factors are present.
If you have kidney disease or another relevant medical condition, ask a healthcare professional whether your pain medicine is appropriate for you.
Can painkiller-related kidney problems happen suddenly?
Yes. Acute kidney injury can develop over a relatively short period, particularly when kidney blood flow is compromised.
For example, NSAIDs may contribute to acute kidney injury when someone is dehydrated because of vomiting, diarrhoea, fever or poor fluid intake.
Kidney damage can also develop more gradually with prolonged or excessive exposure to certain pain medicines.
How long can kidney side effects last?
There is no single answer.
Some acute kidney problems can improve when the underlying cause is identified and treated, while other kidney damage can be prolonged or permanent. The outcome depends on the type and severity of injury, existing kidney health and other medical factors.
A healthcare professional may need blood or urine tests to determine whether kidney function has actually been affected.
Should I stop my painkiller if I think it is affecting my kidneys?
Do not make changes to prescription medication without appropriate medical advice unless you are being treated for an emergency and instructed to do so by a healthcare professional.
If the medicine is non-prescription, speak to a pharmacist or doctor promptly about the suspected reaction and what pain-management options are suitable for you.
If you have severe symptoms, signs of an allergic reaction, a suspected overdose or rapidly worsening illness, seek urgent medical help.
What are the most important things to know about painkillers and kidney side effects?
The key points are:
- NSAIDs are the painkiller group most commonly associated with reduced kidney blood flow and acute kidney injury.
- Existing kidney disease, dehydration and certain other medicines can increase risk.
- Kidney problems may cause few symptoms initially.
- Reduced urination, swelling, blood in the urine, persistent vomiting, confusion or shortness of breath deserve medical attention.
- Do not diagnose kidney damage from symptoms alone.
- Check active ingredients so you do not unintentionally duplicate pain medicines.
- Do not stop prescription medicines or alter treatment without professional guidance.
- Speak to a doctor or pharmacist if you are worried about regular painkiller use or possible kidney side effects.
When to speak to a healthcare professional
Contact a doctor or pharmacist if you develop an unusual symptom after starting or regularly using a painkiller, particularly if you have kidney disease or another condition that could increase your risk.
Bring a list of everything you take, including prescription medicines, OTC painkillers, cold and flu products, supplements and herbal products.
For severe symptoms, suspected overdose, difficulty breathing, face or throat swelling, fainting, seizures, severe bleeding, very low urine output, severe shortness of breath or rapidly worsening illness, seek urgent medical care.
This information is for general education and cannot determine whether a particular painkiller is causing your symptoms. A doctor or pharmacist can assess your medicines, health conditions and, where necessary, kidney-function tests to advise you safely.